International Journal of Computer Applications (0975 – 8887)
Volume 178 – No. 48, September 2019
10
Accurate and Cost-Effective Mini CNC Plotter
Sara Raad Qasim
Computer Engineering, Alfarabi
University
Baghdad, Iraq
Haider Mohammad
Computer Engineering, Alfarabi
University
Baghdad, Iraq
Mustafa Falah
Computer Engineering, Alfarabi
University
Baghdad, Iraq
ABSTRACT
A Computer Numerical Control (CNC) plotter machine is a
computerized numerical control machine which can be used to
draw anything or design any mechanical parts according to
the design program. The utilization of CNC machine is
increased rapidly due to the growth of technology in
industries. The fabrication of a low cost CNC plotter becomes
a persistent need. In this paper, a low cost, medium size and
accurate mini CNC plotter is designed using simple and low
cost components: a microcontroller (Arduino), stepper and
servo motors and their control software. Software has been
used to produce a G code for the operation of the system; G
code is an effective language in which people tell the machine
tools ‘How to make something’. G code allows the machine to
sketch the plots by converting the instructions of that plot into
a readable format by the motor driver telling these motors
where to move (the machine in this paper can draw maximum
dimensions 270m*210m) & how fast to move.
Keywords
CNC, MCU, MIT, Arduino UNO, IDE
1. INTRODUCTION
Computer Numerical Control (or CNC) [1] is an advanced
form of automatic machine that used widely to control the
motion of these machine tools. Numerical control machine
was first invented around in 19th century to minimize the load
of the work [2]. Its advantage ensures higher efficiency,
higher flexibility, and low production cost, a little working
time and a little loss in production. It mainly follows three
steps that are receiving data, interpreting them and react
accordingly [3].
To direct the machine function, a special codes and numbers
form sequential commands (instructions) that are used to
operate the machine automatically and to produce a specific
part with specific dimension. These instructions (program) are
then converted in to an electrical signal and act as input to the
motors which run the machine and do the basic
movements[4].
A machine control unit (or MCU) decides the tool depth of
draw, drawing speed etc. Motion of tool is based on Right
hand coordinate system. Three axis of rotation (x, y & z) for
three dimensional motion of tool and for specific role plus an
axis of rotation. The x-axis serves as height stands and uses
two pieces one for front and one for back. The y-axis acts as
motor mount to move z-axis in addition with slide mechanism
whereas the z-axis controls the depth by allowing the
movement of router in up and down direction so it is very
important axis[5][6].
1.1 History of CNC
The idea of numerical control began when the automation of
machine tools originally incorporated specific concepts of
programmable logic [7]. In the beginning, the first machines
were constructed in the 1940s. But more advanced machines
came along in the 1950s. These new NC machines were built
based on existing tools that were modified with motors
designed to move machine's controls. These first mechanisms
were soon improved with both analog and digital
computers[8][9].
After World War II, specifically in 1949, John Parsons found
methods to improve aircraft by creating stiffened skins for
them. This led to important Air Force research projects, which
conducted at the Massachusetts Institute of Technology
(MIT). After the research phases, an experimental milling
machine was designed at MIT. Professor J.F. Reintjes with his
team of researchers were involved in this project.
In the 1960s and 1970, a very familiar form of a CNC
machine started taking shape. Digital technology then entered
the fray, and automation in production processes became
more efficient than ever [10]. Figure 1 shows the first CNC
machine.
Fig. 1: First CNC machine
1.2 The most famous CNC machines
1.2.1 CNC Milling
A CNC milling is a machine process that uses computerized
controls and rotating multi-point cutting tools to progressively
remove material from the workpiece or cut different materials
such as metal, plastic, glass, and wood, and produce a custom-
designed part or product (see Figure 2)[11][12].
Fig. 2: CNC Milling
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1.2.2 CNC Lathes
CNC lathe is a CNC machine that used to cut workpieces as
they are turned. CNC lathe can make exact cuts rapidly by
utilizing different apparatuses (see Figure 3). The result is a
beautifully finished product so that these machines are very
successful in the exactness they offer contrasted with manual
lathe. They are used by many industries to include
automotive, electronics, aerospace, firearm manufacturing,
sporting, and much more [13].
Fig. 3: CNC Lathe Machine
1.2.3 CNC Routers
A CNC router is very similar in concept to a CNC milling
machine. It is a computer-controlled cutting machine related
to the hand-held router used for cutting various hard materials,
such as wood, composites, aluminium, steel, plastics, glass,
and foams. CNC routers (shown in Figure 4) can perform the
tasks of many carpentry shop machines such as the panel saw,
the spindle moulder, and the boring machine. They can also
cut mortises and tenons. CNC router diminish waste and
increment efficiency, creating different things in a
considerably shorter measure of time than utilizing different
machines [14].
Fig. 4: CNC Router
1.2.4 CNC Plasma Cutters
A CNC plasma system is a machine that carries a plasma
torch, and can move that torch in a path directed by a
computer. The procedure of plasma cutting includes the
cutting of a material utilizing a plasma burn. This strategy is
most ordinarily used to cut overwhelming materials, for
example, steel and different types of metal. CNC plasma
cutter is shown in Figure 5 [15].
Fig. 5: CNC Plasma Cutter
1.2.5 CNC Electric Discharge Machines
Electric discharge machining, or EDM for short (see Figure
6), includes making a particular shape inside a specific
material by utilizing electrical releases, or starts. The material
is expelled from a particular workpiece by a progression of
repeating electrical releases between two anodes. These
anodes are isolated by a dielectric liquid, which regularly gets
an electric voltage [16].
Fig. 6: EDM
2. MAIN COMPONENTS OF MINI CNC
PLOTTER
The block diagram of mini CNC plotter is shown in Figure 1:
Fig. 1: Simple block diagram of mini CNC plotter
2.1 Input Device
The input device is a computer that uses specific software to
draw any design. These software will be explained section 4
(project software).
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2.2 Interface
Interface Unit contains many components that help in
programming and interfacing the input device into the
sketching unit. These components include:
1. Two Stepper Motors
2. Two A4988 Stepper drivers
3. One MG 90S Micro Servo motor
4. CNC v3 shield
5. Arduino Uno R3
2.2.1 Stepper Motor
A stepper motor is a brushless DC electric motor that divides
a full rotation into a number of equal steps (see Figure 2).
Stepper Motors represent the heart of CNC plotter. Two
stepper motors are used for x and y axis for precise control
over drawing pen (sketching unit) for object sketching. They
have important role such that they control the size and type of
speed, accuracy, CNC router precision etc. [17].
Fig. 2: Stepper Motor
The axis of CNC machine (x, y & z) is based on the right
hand coordinate system (rotation is counter clockwise about
the axis of rotation as shown in Figure 3) [18].
Fig. 3: The CNC axes
2.2.2 Stepper Driver
Stepper motor drivers (as shown in Figure 4) are specifically
designed to drive stepper motors, which are capable of
continuous rotation with precise position control, even
without a feedback system. They offer adjustable current
control and multiple step resolutions, and they feature built-in
translators that allow a stepper motor to be controlled with
simple step and direction inputs. In this project we use two
drivers for the two stepper motors [17].
Fig. 4: Stepper Driver
2.2.3 Servo Motor
Servo motor controls the up and down movement of drawing
pen in z axis direction It controlled by sending an electrical
pulse of variable width, or Pulse Width Modulation (PWM)
and this can be achieved using the microcontroller. It
determines the position of the shaft, through the control wire,
which represent the z axis [19].
Fig. 5: Servo Motor
2.2.4 CNC Shield
CNC shield V3.0 can be used as drive expansion board for
engraving CNC machine. It has 4 slots in the board for stepper
motor drive modules that can drive 4 stepper motors. Each
stepper motor need two IO port only, that is to say, 6 IO ports
can quite well to manage three stepper motors as shown in
Figure 6. It is very convenient to use with the microcontroller
(Arduino) such that it is placed above the Arduino [20].
Fig. 6: CNC Shield
2.2.5 Arduino
Arduino Microcontroller (Here Arduino Uno is used as shown
in Figure 7) controls the position of the stepper motors with
the help of program instructions. This microcontroller is an
open source platform based on both hardware and software
that very easy to use. It has 14 digital and 6 analog
input/output pins that can incorporate into various expansion
boards [21][22].
Fig. 7: Arduino Uno
Arduino programs are written in C++ programming language
with a compiler that produces binary machine code.
2.3 Sketching Unit
Sketching Unit is the output unit and it comprises a drawing
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pen or pencil and will be controlled by the three motors.
3. PROJECT CONNECTIONS
To build the base of CNC, several wooden pieces are cut
which have made holes and blind holes and a wooden table
(40cm * 40cm table is used in this paper) which form the base
and support of the machine. The screwed steel rods (which
were taken from an old wardrobe sliding door) operate as a
worm drive. The blind holes serve as a stop for the steel bars
that act as guides for the x-axis. In the middle, the screwed
steel bar was put, that when turning, generates displacement
in the x-axis as shown in the figures below:
Fig. 8: Project Connections
The electronic connections include the connection of the
stepper motor driver above the CNC shield then placing the
CNC shield above the Arduino as shown in Figure 9. For
simplicity two drivers were used for the two stepper motors
(marked by 1 and 2 in Figure 9).
Fig. 9: Stepper Drivers with CNC Shield Connection
Other complementary components must be connected to the
CNC shield as shown in Figure 10.
Fig. 10: CNC shield Connection
The final completed project is shown in Figure 11.
Fig. 11: Final Project Connection
4. PROJECT SOFTWARE
At the beginning all the required software must be setup in the
input unit (the computer). First Inkscape software was used
which converts images or text into a code called G code. G
code is a special code that consists of the dimensions of the
image (x, y, z) and such that it gives the way that the motors
move from one point to another and at specified speed. Then
the simulator or G Code sender was used. It communicates
with the CNC machine through the com port of the computer
which connected it with the microcontroller (Arduino) (com3
was the port in this design). Through the G Code sender the
image is opened as a link (by the Inkscape) and sent it to the
CNC machine. Finally the IDE software must be used to
program the Arduino. This program acts only as interface
through which the code is uploaded to the Arduino and knew
the com port.
4.1 Inkscape
Inkscape (see Figure 12) is a free and open-source graphics
editor. It is professional quality vector graphics software
which runs on Windows, Mac OS X and GNU/Linux. It is
used for creating G code for a wide variety of graphics such as
illustrations, icons, logos, diagrams, maps and web graphics
[23].
Fig. 12: Inkscape Software
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4.2 Simulator - G Code Sender
G Code Sender is a GRBL compatible, cross platform CNC
control software. Its features a highly optimized and
asynchronous (event-driven) UI and USB-to-Serial
communication and can be also used on computers with small
amount of RAM and CPU. It is used to transfer G Code files
to CNC machines running G Code interpreters (3D printers,
milling machines ...etc) (see Figure 13) [24].
Fig. 13: Simulator Software
4.3 Integrated Development Environment
(IDE)
Arduino IDE is a piece of free software that enables users to
program in the language that based on C/C++ and can even be
extended through C++ libraries. The IDE (see Figure 14)
enables users to write a computer program, which is a set of
step-by-step instructions that you then upload to the Arduino.
Arduino will then carry out those instructions and interact
with whatever you have connected to it. In the Arduino world,
programs are known as “sketches” [25].
Fig. 14: IDE Software
5. PROJECT PROGRAMMING SCHEME
Figure 15 shows the project scheme in simple manner. It also
provides a complete understanding of the whole project
software and their roles.
Fig. 15: Simple Project Scheme
6. CONCLUSION
In this project, Small drawing machine or mini CNC was
built. It is a digital electromechanical machine with digital
control through a piece of wood and low cost components.
Two main axes (x & y) and a vertical axis (z) were used to
draw image or figure with a specific dimension and speed.
This project design was success prototype design since it can
draw any figure or image easily and in a short time as
compared to human drawing time.
7. ACKNOWLEDGEMENTS
The authors gratefully acknowledge Alfarabi University of the
pacific for their CNC project. The following individuals have
assisted the authors in gathering information and photos for
his research on CNC. With thanks, they are Omer Amer and
Abdulla Jamal.
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